THE tsunami’s devastation on the Indian Ocean’s shores offers a strategic lesson of incomparable importance. Whether or not the Pentagon’s current leadership is capable of grasping that lesson is another matter.

The Indian Ocean and its adjoining seas and gulfs form one crucial, integrated strategic theater. The region has been critical to Western dominance for five centuries. Yet, when our intelligence services or military planners consider this vast, densely populated region at all, they poke at the different parts and miss the whole.

The Indian Ocean theater contains the world’s largest democracy (India), the world’s most populous Muslim state (Indonesia), the greatest concentration of oil (on the Arabian Peninsula and in the Persian Gulf), the first Muslim nuclear power (Pakistan), the most progressive economies in Southeast Asia (Singapore, Malaysia and Thailand) and the greatest concentration of terrorists in the world.

On its eastern extreme, this vast region is bounded by Australia, a sturdy Western outpost. To the west, the Indian Ocean laps the old Swahili Coast and the Republic of South Africa, a state on its way to becoming the continent’s first indigenous great power.

No region of the world is so complex, or so thick with both threats and opportunities. The Indian Ocean region is not only critical in detail, but has an overall importance even greater than its parts. From the vital sea lanes that once carried spices and now carry oil, to the competing civilizations on its littorals, the Indian Ocean binds together the world’s great passions, needs and dangers.

This is where Islam must – and can – change; where nuclear weapons are likeliest to be used; where the future economic potential is vast; where the bulk of the world’s heroin is produced; and where the heroin of the world economy – oil – could be cut off with a handful of nuclear weapons (think Iran, the Suez Canal and a few Arab ports).

We have failed to see the forest for the palm trees. Nature recognized what our government consistently fails to understand. The earthquake centered off the coast of Sumatra triggered deadly waves that struck Thailand and Somalia, India and Indonesia, Burma and the Maldives, Sri Lanka and Africa’s Swahili coast.

The tsunami drew a strategic map of the 21st century. It took a tragedy to inspire serious American involvement in the region (apart from the Middle East, with which we remain rabidly obsessed). While cognizant of the horrors that brought them to Indonesia, U.S. Navy officers are relieved to have a mission at last. Largely excluded from participation in Iraq and Afghanistan because of the reactionary choices the service made, our Navy has suffered from a perception of fading relevance.

Yet, our Navy remains as important to America’s security as it ever was. The problem is that the Navy itself can’t see it. The service suffers from the destructive nostalgia that afflicted the Army a decade ago, the desire to perfect a force to fight the wars of the past.

Nonetheless, our Navy remains the lead service for security affairs in the Indian Ocean. The Air Force will have a role in crises, while the Army and Marines will be needed to fight the region’s ground campaigns of tomorrow (they’re coming), but our naval presence is the indispensable military and strategic tool required by the Indian Ocean’s strategic environment.

We have lost our focus on the control of the seas.

Half a millennium ago, the Indian Ocean proved to be the soft underbelly of the Ottoman Empire. Obscure naval battles off the coast of India secured the spice routes for Europe and triggered the long Ottoman decline. Today, the Indian Ocean is the weak link in Western security, a distant theater whose sea lanes carry not only oil, but vital trade, from the Suez Canal to the Straits of Malacca. No other region is so critical and so vulnerable. If we look beyond the terrible toll of the tsunami, there is much to be hopeful about. Far too little attention has been paid to the Thai government’s position that, while it welcomed foreign recovery expertise, it did not need post-tsunami financial aid. Only a generation ago, Thailand was dirt-poor; today, it’s proud of its ability to self-recover.

India has become a prized source of top-flight human capital. Afghanistan’s proving that democracy can work in the absence of superhighways and investment bankers. South Africa is pioneering a dynamic multiracial society on a continent old-school thinkers blithely write off. And Indonesia, for all its problems, relishes its new democracy and its tolerant forms of Islam.

The future is waving its arms and shouting, but we see only the past.

First in uniform, then as a civilian, I’ve visited most of the countries on the Indian Ocean littoral, from Burma to Mozambique. I’ve become convinced both of the need to view the region as a unity and of the criticality of intelligent American engagement.

Only last month, I completed a book (“New Glory,” due out next summer) that argues for a shift in our strategic priorities and a fundamental rethinking of the way we view the world. My conclusion was that the Indian Ocean lies at the heart of postmodern strategy. I didn’t expect the disaster of the century to underscore my point.

The tsunami’s devastation raised a signpost to the 21st-century’s future. Does our government have the strategic literacy to read it?